Date: 1992

Grade(s): 4, 5, 6

Subject(s):

• Science/Astronomy

1. Name and locate five common constellations.
2. Write an original myth about a favorite constellation or group of stars

Introduction

There are billions of stars in the sky, yet on the clearest of nights away from city lights you will only be able to see about 3,000. Many more stars are even further away, too faint to be seen even by our telescopes. The closest star to Earth is the sun. It is the center of our solar system.

Stars form when gas and dust are pulled together by the force of gravity. This is the same gravity that pulls a ball you have thrown into the sky back to the earth. Sometimes tiny differences in the pull of gravity forms regions of trapped gas and dust called nebula. These nebula are like star incubators. As these dust and gas particles are pulled together even more, the nebula's temperature increases.

Eventually the temperature gets so hot that the gas and dust particles move at incredibly high speeds. (Remember how water starts to move or boil as it is heated? This is the same principle.) At these high speeds the atoms of these gases may crash and form a single nucleus. This is called fusion. The hot gases push outward and the gravity pulls inward. When this pushing forms a balance a star develops. Energy from the fusion reaches the surface of the star and shines into space.

Usually stars form in pairs. These stars then orbit each other. They are called double stars. Sometimes even three or four stars are formed together and orbit each other. At other times stars may form alone like our sun.

Stars last a long time. Small to average size stars shine for about 10 billion years. More massive stars may shine for only a million years because they shine so brightly and use up their mass more quickly than smaller stars.

When ancient peoples studied the skies they often imagined that the stars formed pictures of people, animals or objects. These groups of stars are called constellations. They then made up stories or myths to go along with these constellations.

The ancient Greeks named 48 constellations. We still use these constellations to describe portions of the sky. Few of these constellations actually look like a figure. Orion is one that does resemble a hunter if you draw lines to connect the stars.

Native Americans also made up stories about the stars. The Greeks called the pattern of seven bright stars in the northern sky a bear. The Coeur d'Alene Indians who lived in northern Idaho also thought of this constellation as a bear, a grizzly bear. Their myth for this constellation says that once there were three brothers who had a grizzly bear for a brother-in-law. The youngest brother liked him but the two older brothers didn't like him at all. They were all on a hunting trip and the two older brothers told the youngest that they planned to kill the brother-in-law. The youngest brother couldn't let his brothers kill the brother-in-law so he crept away to warn him. The brothers followed the youngest closely. They were just ready to shoot their arrows when the youngest looked back and shouted that the brother-in-law was about to be shot. Just as he said it all four were taken into heaven and transformed into the stars of the bear. We know this constellation as the Big Dipper. (Monroe, Jean. They Dance in the Sky. Boston: Houghton Mifflin. 1987.)

The Big Dipper is one of the brightest and most easily found constellations. It is almost always visible in some part of the sky. Find the Big Dipper on a clear night. You might need to use a star chart. The two stars forming the outside edge of the cup or dipper are called pointer stars. They point to Polaris, the North Star. The distance from the pointer stars to Polaris is five times the distance between the two pointer stars. The Little Dipper forms off Polaris. Polaris is the end star in the Little Dipper's handle. If you enjoy looking at the sky you may want to join the Skywatchers' Club.

Class Activity 1 - Skywatchers' Club

You may want to form a Skywatchers' Club with students around the country that are also interested in astronomy or working on this unit.

Class Activity 2

Materials:

1. Overhead projector
2. Masters of constellations (See diagrams 3 - 12 in the Teacher's Aid Book)
3. Construction paper
4. Sharp scissors or other instruments to make holes in the paper

1. A kind of classroom planetarium can be made by placing a piece of construction paper with holes punched strategically on it to form the shape of a constellation on an overhead projector in a darkened room. Students may help make these overlays, using the masters of the constellations from the Teacher's Aid Book.

2. The other students can discuss what the star patterns look like. They might want to connect the stars with chalk if projected on a blackboard. Point out where in the sky they would have to look to find each constellation.

3. Teacher's Note: This activity should proceed the student writing activity as a kind of warm-up exercise.

Materials:

1. Pencils
2. Paper for writing and drawing

Choose a constellation or make up your own constellation, using stars that actually exist, and putting them together in a new pattern. Think about what shape the pattern of these stars form. Also tell how did this pattern of stars get into the heavens. Now write your own story about the constellation. Be sure to include at least one drawing of the constellation and write your name on it. It may help for you to pretend that you are telling a story to a young child about how these stars got into the sky. You can be as fanciful or realistic as you wish.

Student Activity 2 (Optional): Constellation Viewer

Materials:

1. potato chip cans
2. piece of cardboard
3. hammer
4. nail
5. scissors
6. pins
7. stapler
8. white crayon
9. black construction paper

Using a hammer and nail, make a hole in the center of the end of the can. Using the lid as a pattern, trace circles on the black paper to fit on the open end of the can. With the straight pin, punch holes through the paper for each star in the constellation. Cut out the circles of black paper. Place the circles one at a time inside the lid and fasten to the can. Look through the hole in the end of the can to view the constellation. You may want to cover the outside of your tube with black paper, label and decorate.

Student Activity 3

While much of the energy that radiates from stars is light, other energy is also radiated. Even though it is invisible, we can prove that it exists. William Herschel proved the existence of infrared radiation. You can copy his experiment. (From NASA's "Seeing in a New Light" )

Materials:

1. prism
2. three weather thermometers
3. light source
4. pencil and paper

Procedure:

1. Allow the three thermometers to register the temperature of the air where the experiment will be done - about 5 minutes. Take careful note of the temperatures.

2. Create a spectrum with the prism using sunlight as the light source. Visible light can be broken like a rainbow into colors of the spectrum.

3. Place thermometers at several points in the spectrum: one in the violet range, one in the center, and one just barely beyond the red end. Then leave the thermometers in the spectrum for at least 5 minutes, moving them carefully as the sunlight moves the spectrum. Temperature changes may be very slight, so observe carefully.

   Questions:

   1. What were the final readings on each of the three thermometers?
   2. Why would there be an increase in temperature beyond the red end of the spectrum?
   3. What does this tell us about what exists beyond the visible red?

Teacher's Note: This activity requires blueprint paper.

Description:

To demonstrate the existence of ultraviolet radiation, another kind of invisible radiation, and duplicate Ritter's experiment. In 1801, Johann Ritter performed an experiment using paper treated with silver chloride, which decays in the presence of light. He found that the silver chloride deteriorated even more rapidly when exposed to the previously unknown radiation beyond the violet end of the spectrum.

(From NASA's "Seeing in a New Light" )

Materials:

1. several sheets of blueprint paper
2. 1 qt of household ammonia
3. flat pan
4. prism or mirror in pan of water
5. light source

Using a prism or a pan of water, create a spectrum on a horizontal surface, such as a table. Use sunlight from an open window, as glass blocks most ultraviolet radiation. The prism should be resting on a stable object so that the spectrum does not move.

Working quickly to prevent exposure of the paper to too much light, cut a piece of blueprint paper about four times larger than the spectrum. Place the blueprint paper, which behaves the same way that Ritter's silver chloride paper did, underneath the spectrum. Quickly outline the area covered by the spectrum with a felt-tip pen. Label the violet end.

NOTE: Depending on the sensitivity of the paper, different exposure times will be needed. Most exposure times will be fairly brief - about 15 to 20 seconds.

Put just enough ammonia in the pan to cover the bottom to a depth of about 0.5 in. or (1 cm). In front of an open window or beneath a vent fan, hold the paper over the pan of ammonia so that the fumes will process the paper. Notice the changes in the area outlined and the area just beyond the violet end. You may have noticed that this area began to change even before processing with the ammonia.

Questions:

1. What happened to the part of the paper lying where you can see violet?
2. What happened to the part of the paper lying just beyond that violet section?
3. What does this demonstrate about the area beyond the violet end of the spectrum?

Enrichment

Adapted from Scott Foresman, Discover Science 5, 1991.

Teacher's note: This activity uses diagram 13 from the Teacher's Aid Book.

The stars in a constellation seem to be close together because they all seem to be located in the same direction. They may appear to be near each other but they really are far apart in space. They can be thousands of light years apart. (This is a way to measure distances of stars that you will learn about in week four.)

These stars are traveling in different directions through space too. This means that the positions of the stars in a constellation change. Scientists can predict changes based on the estimated speeds and directions of their movement.

Use copies of the star prediction chart (diagram 13) included in the Teacher's Aid Book. This will help you understand how astronomers make these predictions.